The development of transmitting media having a large wideband characteristic, e.g. in the form of glass fiber circuits over which laser beams are transmitted as information carriers, has led to proposals to introduce a complete decentralized switching system into pulse code modulated (PCM) time-division multiplex telecommunication networks.
In a solution of this kind known in the art (West German Unexamined Disclosure Publication No. 1,804,624), the basic form of the communication network comprises a number of subscriber line circuits linked together by a directional transmission line closed in the form of a loop. This loop comprises as a single central member a clock station, the function of which is to determine a number of time multiplexors in the loop. In order to be able to establish a connection, the subscriber stations monitor, by means of individual detectors, the time slots for the appearance of an idle-channel signal. Upon the detection of an idle-channel, they occupy it by means of a synchronizing circuit likewise allocated to individual subscribers and periodically connected to the line during the time interval constituting the channel. The called subscriber detects with the aid of an address detector his address transmitted in the occupied time slot from the dialing subscriber station and ensures with the aid of his synchronizing circuit that he is connected periodically to the transmission line during the time intervals constituting the channel.
Another known technique when employing a wideband transmitting medium is to switch in a decentralized way, such that the subscriber line circuits disconnect the portion of the entire flow of information fed to each subscriber and intended for them by virtue of the destination address transmitted at the same time (see, e.g., NTZ Report 14, 1972, pp. 23- 26). However, in this case, too, central equipment is still needed, viz. storages disposed in the network junctions designed for the prevention of undue superimposition of message blocks entering the junctions from various directions.
Thus, the advantages resulting from decentralized switching and residing mainly in the fact that a communication network operated in this fashion can be expanded without having taken appropriate measures for future expansion originally are regated by the large amount of components for the subscriber line circuits and by the fact that the advantages are not fully utilized, because, as mentioned above, central facilities cannot fully be dispensed with. However, even if one adheres to a centralized end exchange because of the above or other reasons, the possibilities offered by wideband transmitting media can be used to advantage.
An object of the invention is to provide a method of operation for a PCM time-division multiplex telecommunication network in which the through-connection to receiving subscriber stations occurs as a result of destination addresses interpreted at the receiving end, in which the expenditures for equipment allocated to individual subscribers and in which synchronization difficulties during the switching process are avoided.